1. Field of the Invention
The present invention relates to a thermal transfer device, and more particularly to a thermal transfer device used for forming a light modulator or a display device.
2. Description of the Related Art
Cost issue has become more and more crucial in the development of display devices, especially under driven by the application of LCD televisions. Inkjet printing has been developed for the sake of cost saving. Not only saving the material, but also it can directly pattern desired areas for particular purposes. However, the precise droplet control is seriously concerned in inkjet printing. Controlling the printing direction of the droplets flowing through the air strictly challenges the print head and the recipe. Thermal transfer is another technology similar to the printing technology. If the material having been transferred is well controlled, it is worthy to develop the thermal transfer technology in the application of the display devices.
In the known thermal transfer technology, U.S. Pat. No. 5,216,438 provides a direct color thermal printing method for optically and thermally recording a full-color image on a thermosensitive recording medium. FIG. 1 shows an example of the thermosensitive recording medium 10 in which a thermosensitive recording layer 12, which is developed in a cyan color, a thermosensitive recording layer 13, which is developed in a magenta color, a thermosensitive recording layer 14, which is developed in a yellow color, and a protective layer 15 are laminated on a supporting material 11 in the order from the bottom. The thermosensitive recording layer 12 develops cyan when a predetermined amount of heat energy per unit area is applied thereto. The thermosensitive recording layer 13 contains a diazonium salt compound having a maximum absorption factor at a first specific wavelength and a coupler which acts upon the diazonium salt compound and develops magenta when it is heated. The thermosensitive recording layer 13 loses its capacity to develop color when it is exposed to the ray with the first specific wavelength, because the diazonium salt compound is photo-chemically decomposed by the ray. The thermosensitive recording layer 14 contains a second diazonium salt compound having a maximum absorption factor at a second specific wavelength and a coupler which acts upon the second diazonium salt compound and develops yellow when it is heated. The thermosensitive recording layer 14 is also optically fixed and loses its color developability when it is exposed to the ray of the second specific wavelength. A cyan image is recorded in the thermosensitive recording layer 12 by applying appropriate heat energy thereto. Making use of this heat energy, the thermosensitive recording layers 13 and 14 having optically recorded images are thermally developed, whereby the diazonium salt compounds remaining in these layers couple with the couplers and thus develop magenta and yellow colors. The recording medium 10 thus has a full-color image thereon.
U.S. Pat. No. 6,228,555 disclosed a thermal mass transfer donor element as shown in FIG. 2, in which the donor element 106 includes a donor substrate 110, a light-to-heat conversion (LTHC) layer 112, a thermal transfer layer 114, and an underlayer 118 disposed between the donor substrate 110 and the LTHC layer 112. By placing the thermal transfer layer 114 of the donor element 106 adjacent to a receptor substrate (not shown) and irradiating the donor element 106 with image radiation that can be absorbed by LTHC layer 12 and converted into heat, material can be transferred from the thermal transfer layer 114 to the receptor substrate to form patterns of the transferred material thereon.
U.S. Pat. No. 6,031,586 disclosed a printing apparatus for radiation thermal transfer of colorant from a donor to a receiver, including a flash tube for emitting high intensity radiation, a polarizer for receiving high intensity radiation from the flash tube and polarizing such radiation, and liquid crystal cells disposed to receive polarized radiation from the polarizer. Electrodes modulate the liquid crystal cells so that they change polarization of the radiation passing through them. A second polarizer receives radiation from the liquid crystal cells and is arranged to pass different intensities of radiation depending on their polarization. The colorant donor and the receiver are positioned in colorant transfer relationship with the second polarizer at a colorant position so that radiation which passes through the second polarizer illuminates the colorant donor so that colorant is transferred to the receiver.